1. Field of the Invention
The invention relates to an injector of an injection system, having a high-pressure connection chamber (common rail) and an injection nozzle protruding into the combustion chamber of an internal combustion engine. It has proved advantageous that the pressure prevailing in the high-pressure connection chamber is not applied permanently to the injection nozzle of an injection system but instead is controllable via a separate control part. There is a need to keep the control volume of the fuel, which is at very high pressure, as small as possible.
2. Prior Art
From German Patent Disclosure DE 198 35 494 A1, a unit fuel injector with which fuel can be injected into a combustion chamber of a direct-injection internal combustion engine is known. The unit fuel injector includes a pump unit for building up an injection pressure for injecting the fuel into the combustion chamber via an injection nozzle. A control unit is provided, which includes a control part. A valve actuating unit is also provided, which serves to control the pressure buildup. To furnish a unit fuel injector of simple design and small size which in particular has a short response time, the valve actuating unit is embodied as a piezoelectric actuator. In the configuration of the prior art, the valve actuating unit is mounted laterally on the injector and thus requires additional installation space at the cylinder head of an internal combustion engine, space that is extremely scarce at that location.
With the version according to the invention, there is the advantage on the one hand of a substantially more compact structure. A separate supply line from the high-pressure connection chamber (common rail) to the control part can be dispensed with, since the control part is now disposed in a space-saving way in the interior of the high-pressure connection chamber. Pressure pulsations in the line system are not transmitted to the injection nozzle which performs the injection, and which protrudes into the combustion chamber of the engine and meters the injection quantity. Postinjections can thus be effectively counteracted.
On the other hand, with the version proposed by the invention it can be attained that the control volume remains small. By means of an inlet throttle discharging from the high-pressure connection chamber into the control chamber, a partial volume of fuel that is sufficient to trigger the control part is always present, so as to assure triggering of the control part that partially penetrates the high-pressure connection chamber. The control part is acted upon by a sealing spring, which in the closed state of the control part assures that the control part is pressed against a seat face of the housing of the high-pressure connection chamber, thus assuring effective sealing off of the high-pressure connection chamber from the valve chamber.
The control chamber is provided in the portion of the control part that is located in the hollow space of the high-pressure connection chamber. The inlet throttle to the control chamber likewise discharges into this hollow space. On the outlet end of the force-balanced valve control part in the hollow chamber of the high-pressure connection chamber, an outlet throttle is provided, which discharges into a seat face; the seat face is closed by a sealing element, which for example is embodied in the form of a ball. The control valve on the outlet side can be actuated via an electromagnet, or a piezoelectric actuator, to relieve the control chamber in the control part.
Below the valve chamber in the valve housing, a leaking oil chamber is provided, from which a leaking oil rail branches off. The leaking oil rail is closed via one or more releasable closures and can be evacuated by way of them. Besides an individually performable evacuation at the various closures, it is also possible for the leaking oil rail to be designed such that it discharges into the fuel tank.
By means of the seat faces for the control part that are embodied on the housing of the injector and by means of the control edge embodied on the control part, the valve is closed on the leaking oil side, in the open state. The high-pressure connection chamber is thus effectively secured against direct communication with the leaking oil chamber.